Multiple component solid state white light

ABSTRACT

A white light emitting lamp is disclosed comprising a solid state ultra violet (UV) emitter that emits light in the UV wavelength spectrum. A conversion material is arranged to absorb at least some of the light emitting from the UV emitter and re-emit light at one or more different wavelengths of light. One or more complimentary solid state emitters are included that emit at different wavelengths of light than the UV emitter and the conversion material. The lamp emits a white light combination of light emitted from the complimentary emitters and from the conversion material, with the white light having high efficacy and good color rendering. Other embodiments of white light emitting lamp according to the present invention comprises a solid state laser instead of a UV emitter. A high flux white emitting lamp embodiment according to the invention comprises a large area light emitting diode (LED) that emits light at a first wavelength spectrum and includes a conversion material. A plurality of complimentary solid state emitters surround the large area LED, with each emitter emitting light in a spectrum different from the large area LED and conversion material such that the lamp emits a balanced white light. Scattering particles can be included in each of the embodiments to scatter the light from the emitters, conversion material and complimentary emitters to provide a more uniform emission.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to light emitting diodes (LEDs) and moreparticularly to an apparatus with multiple LEDs that in combinationproduce white light.

2. Description of the Related Art

Light emitting diodes (LEDs) are an important class of solid-statedevices that convert electric energy to light. They generally comprisean active layer of semiconductor material sandwiched between twooppositely doped layers. When a bias is applied across the doped layers,holes and electrons are injected into the active layer where theyrecombine to generate light. Light is emitted omnidirectionally from theactive layer and from all surfaces of the LED. Recent advances in LEDs(such as nitride based LEDs) have resulted in highly efficient lightsources that surpass the efficiency of filament-based light sources,providing light with equal or greater brightness in relation to inputpower.

One disadvantage of conventional LEDs used for lighting applications isthat they cannot generate white light from their active layers. One wayto produce white light from conventional LEDs is to combine differentwavelengths of light from different LEDs. For example, white light canbe produced by combining the light from red, green and blue emittingLEDs, or combining the light from blue and yellow LEDs.

One disadvantage of this approach is that it requires the use ofmultiple LEDs to produce a single color of light, increasing the overallcost and complexity. In addition, the different colors of light areoften generated from different types of LEDs fabricated from differentmaterial systems. Combining different LED types to form a white lamp canrequire costly fabrication techniques and can require complex controlcircuitry since each device may have different electrical requirementsand may behave differently under varied operating conditions (e.g. withtemperature, current or time).

More recently, the light from a single blue emitting LED has beenconverted to white light by surrounding the LED with a yellow phosphor,polymer or dye, with a typical phosphor being cerium-doped yttriumaluminum garnet (Ce:YAG). [See Nichia Corp. white LED, Part No.NSPW300BS, NSPW312BS, etc.; See also U.S. Pat. No. 5,959,316 to Hayden,“Multiple Encapsulation of Phosphor-LED Devices”]. The surroundingphosphor material “downconverts” the wavelength of at least some of theLED light, changing its color. For example, if a nitride-based blueemitting LED is surrounded by a yellow phosphor, some of the blue lightpasses through the phosphor without being changed while a substantialportion of the remaining light is downconverted to yellow. The LED willthus emit both blue and yellow light, which combine to provide a whitelight.

This approach has been successfully used to commercialize white LEDs fora variety of applications such as flashlights, indicator lights, displaybacklighting, and architectural lighting. However, conventional blueLEDs are too dim for many general lighting applications that currentlymake use of filament-based or fluorescent lamps. While improvements inblue LED efficiency and output power would be beneficial in increasingthe light output from white LEDs, a number of other factors exist whichlimit the performance of such devices. For example, phosphor materialshave a finite conversion efficiency, resulting in “conversion loss”since a portion of the absorbed light is not re-emitted as downconvertedlight. Additionally, each time a higher energy (e.g., blue) photon isconverted to a lower energy (e.g., yellow) photon, light energy is lost(Stokes loss), resulting in an overall decrease in white LED efficiency.This reduction in efficiency increases as the gap between thewavelengths of the absorbed and re-emitted (downconverted) lightincreases. Finally, for blue LEDs to emit an output light fluxsufficient for room illumination, the LED chips themselves can becomevery hot, causing damage the component device layers of the LED chipitself, or degrading surrounding encapsulation or downconverting media.

Another disadvantage of the above white light emitter arrangements(red+green+blue LEDs or blue LEDs combined with yellow phosphors) isthat they do not produce the optimal spectral emission necessary forboth high efficacy and high color rendering. Simulations of whiteemitters show that high efficacy and color rendering can be achievedwith an output light spectrum consisting of spectrally narrow emissionin the blue and red regions, with a slightly broader emission in thegreen region.

In the case of the red+green+blue LED lamps, the spectral emission linesof the component LEDs are typically narrow (e.g. 10–30 nm full width athalf maximum (FWHM)). While it is possible to achieve fairly high valuesof efficacy and color rendering with this approach, wavelength rangesexist in which it is difficult to obtain high-efficiency LEDs (e.g.approximately 550 nm). As a result, it is difficult to achieve both highefficacy and high color rendering index with low manufacturing cost andhigh yield. This can be particularly problematic when spectralrequirements call for high efficiency green LEDs, since such LEDs haveonly been realized in the (In, Ga, Al)N system and are typically subjectto low yield and strong wavelength and emission variations withoperating conditions such as drive current and temperature. While moresimplified white lamps may be realized using only two LEDs emitting atcomplimentary colors (e.g. blue, yellow), it is exceedingly difficult toachieve high color rendering coefficients in such lamps, primarily dueto the lack of any red light in the resulting spectrum.

In the case of blue LEDs combined with yellow phosphor, the resultingwhite light is produced without a red light source. Since the resultinglight is typically deficient in one of the primary colors, lampsfabricated in this manner display poor color rendering.

The desired spectrum can be more closely achieved using a combination ofa blue LED with two separate phosphors emitting in the green and redspectral regions, or using an ultra violet LED with red, green and bluephosphors. However, suitable red phosphors having high conversionefficiency and the desired excitation and emission characteristics haveyet to be reported. Even if such red phosphors were available, theywould be subject to significant energy (Stokes) losses due to theconversion of high energy blue or UV photons to lower energy redphotons.

Patent Publication No. U.S. 2002/0070681 A1 to Shimizu discloses an LEDlamp exhibiting a spectrum closer to the desired spectrum. The lamp hasa blue LED for producing a blue wavelength light, a red emitting LED,and a phosphor which is photoexcited by the emission of the blue LED toexhibit luminescence having an emission spectrum wavelength between theblue and red wavelength spectrum. The phosphor is preferably a yellow orgreen emitting phosphor and in the embodiments shown, the phosphorcovers both the red and blue LEDs.

One of the disadvantages of the Shimizu lamp is that blue LEDs are notas efficient as other LEDs emitting at other wavelength spectrums and alimited number of phosphors are available for luminescence from a bluewavelength of light. Another disadvantage is that with red and blue LEDsplaced side by side, the projected light may have an asymmetricappearance such that the light appears red on one side and blue on theother. Since phosphor particles typically must be on the order of atleast a few microns diameter to achieve high conversion efficiency(i.e., much larger than the wavelength of blue or yellow light) andparticles which are larger than the wavelength of light are poorscatterers, covering one or both of the LEDs with phosphor generallydoes not adequately scatter the LED light to combine the differentwavelengths. This can be a particular problem with large area LEDs usedfor high power, high output.

Another disadvantage of a number of the embodiments disclosed in Shimizuis that they show blue and red LEDs placed on top of one another andthen covered by the phosphor. This can result in the shorter wavelengthblue light being absorbed by the component device layers (e.g., activelayers, metallization layers) of the red LED device, thereby decreasingthe overall efficiency of the lamp. Also, by covering the red LED withphosphor some of the phosphor particles may absorb some of the redlight, which can result in a loss of efficiency because it is generallynot possible to “up-convert” the absorbed red light to higher energygreen light in an efficient manner.

Shimizu also discloses an optical lens as part of its lamp, with theinside surface of the lens being roughened to increase mixing of the LEDlight. Such approaches are generally not effective and can decreaseefficiency by interfering with the purpose of the lens, which is toreduce backscattering of light at the lens/air interface and possiblesubsequent re-absorption within the body of the lamp or LED.

Solid-state semiconductor lasers convert electrical energy to light inmuch the same way as LEDs. They are structurally similar to LEDs butinclude mirrors on two opposing surfaces, one of which is partiallytransmissive. In the case of edge emitting lasers, the mirrors are onthe side surfaces; the mirrors provide optical feedback so thatstimulated emission can occur. This stimulated emission provides ahighly collimated/coherent light source. A vertical cavity laser worksmuch the same as an edge emitting laser but the mirrors are on the topand the bottom. It provides a similar collimated output from its topsurface. Some types of solid-state lasers can be more efficient thanLEDs at converting electrical current to light.

SUMMARY OF THE INVENTION

The present invention seeks to provide solid-state white emitting lampswith high efficacy and good color rendering. One embodiment of a whitelight emitting lamp according to the present invention comprises a solidstate ultra violet (UV) emitter (e.g., laser or LED) that emits light inthe UV wavelength spectrum. A conversion material is arranged to absorbat least some of the light emitting from the UV emitter and re-emitlight at one or more different wavelengths of light. One or morecomplimentary solid-state emitters are included that emit wavelengthspectrums of light that are different than the UV emitter and theconversion material. The lamp emits a white light combination of lightemitted from the complimentary emitters and from the conversionmaterial, with the white light having high efficacy and good colorrendering.

A second embodiment of white light emitting lamp according to thepresent invention comprises a solid-state laser emitting light in afirst wavelength spectrum. A conversion material is arranged to absorbat least some of the light emitting from the laser and re-emits light atone or more different wavelength spectrums of light. One or morecomplimentary solid-state emitters are included that emit wavelengths oflight different than the laser and the conversion material. The lampemits a white light combination of light emitted from the laser,complimentary emitters, and conversion material, the white light havinghigh efficacy and good color rendering. The lamp may also incorporatevarious optics or scattering materials/surfaces to promote mixing anddispersion or mixing and focusing of the component light colors.

Another embodiment of a white light emitting lamp according to thepresent invention comprises a first solid state emitter that emits lightin a first wavelength spectrum. A conversion material is included toabsorb at least some of the light from the first solid-state emitter andemit light at one or more different wavelength spectrums. One or morecomplimentary emitters are included with each emitting light at awavelength spectrum different from said first wavelength spectrum andsaid conversion material wavelength spectrums. Scattering elements (suchas particles, microviods, etc.) are arranged to scatter the light fromthe first emitter, conversion material and complimentary emitters. Thelamp emits a uniform white light combination of light from the firstemitter, conversion material and complimentary emitters.

An embodiment of a high flux white emitting lamp according to thepresent invention comprises a large area light emitting diode (LED) thatemits light at a first wavelength spectrum. A conversion material isarranged to absorb at least some of the light from the large area LEDand re-emit at least one wavelength light in a spectrum different fromthe first wavelength spectrum. A plurality of complimentary solid-stateemitters surround the large area LED, with each emitter emitting lightin a spectrum different from the large area LED and conversion material.The lamp emits a balanced and uniform white light combination of lightfrom the large area LED, conversion material and complimentary emitters.The white light also has high efficacy and good color rendering.

One embodiment of a method for producing white light with high efficacyand good color rendering according to the present invention comprisesgenerating light in the UV wavelength spectrum and passing the UV lightthrough a conversion material that absorbs the UV light and re-emitslight at one or more different wavelength spectrums. The method furthercomprises generating complimentary light at one or more wavelengthspectrums, each of which is different from the conversion materialwavelength spectrums. The conversion material light and thecomplimentary light are combined to generate white light with highefficacy and good color rendering.

Another method for producing white light with high efficacy and goodcolor rendering, comprises generating laser light that is passed througha conversion material that absorbs at least some of the laser light andre-emits light at one or more different wavelength spectrums. The methodfurther comprises generating complimentary light at one or morewavelength spectrums that is different from the wavelength spectrum forthe conversion material light and combining the conversion materiallight and said complimentary light to generate white light with highefficacy and good color rendering.

These and other further features and advantages of the invention will beapparent to those skilled in the art from the following detaileddescription, taken together with the accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of one embodiment of a lamp according to thepresent invention comprising a red LED, a UV LED, and conversionmaterial covering the UV LED;

FIG. 2 is a sectional view of another embodiment of a lamp according tothe present invention that is similar to the lamp in FIG. 1, with theconversion material also covers the red LED;

FIG. 3 is a sectional view of another embodiment of a lamp according tothe present invention comprising a green LED, red LED, UV LED, andconversion material covering the UV LED;

FIG. 4 is a sectional view of another embodiment of a lamp according tothe present invention that is similar to the lamp in FIG. 3, with theconversion material covering all of the LEDs;

FIG. 5 is a sectional view of another embodiment of another lampaccording to the present invention comprising a blue LED, red LED, UVLED, and conversion material covering the UV LED;

FIG. 6 is a sectional view of another embodiment of a lamp according tothe invention that is similar to the lamp in FIG. 5, with the conversionmaterial covering all of the LEDs;

FIG. 7 is a sectional view of another embodiment of a lamp according tothe present invention, with a red LED, blue laser and conversionmaterial covering the blue laser;

FIG. 8 is a sectional view of another embodiment of a lamp according tothe present invention that is similar to the lamp in FIG. 7, with adifferent conversion material covering the blue laser;

FIG. 9 is a sectional view of another embodiment of a lamp according tothe present invention that is similar to the lamp in FIG. 7 or 8, withthe conversion material also covering the red LED;

FIG. 10 is a sectional view of another embodiment of a lamp according tothe present invention comprising blue LEDs covered by a yellowconversion material and two red lasers;

FIG. 11 is a plan view of another embodiment of a lamp according to thepresent invention comprising a large area LED surrounded bycomplementary LEDs;

FIG. 12 is a sectional view of the lamp in FIG. 11, taken along sectionlines 12—12;

FIG. 13 is a sectional view of another embodiment of a white emittinglamp according to the present invention comprising scattering particlesin its conversion material;

FIG. 14 is a sectional view of another embodiment of a lamp according tothe present invention comprising scattering particles in its epoxy;

FIG. 15 is a sectional view of another embodiment of a lamp according tothe present invention comprising a layer of scattering particles; and

FIG. 16 is a sectional view of another embodiment of a lamp according tothe present invention comprising a clear/transparent material betweenthe emitters and conversion material.

DETAILED DESCRIPTION OF THE INVENTION

White Lamp Using UV Emitters

FIG. 1 shows one embodiment of a multi-component solid-state lamp whitelamp 10 constructed in accordance with the invention. It comprises afirst light emitter 12 that emits in the ultraviolet wavelengthspectrum. Alternatively, the first light emitter 12 can emit light inother “short” wavelength spectrums. The emitter 12 is preferably a lightemitting diode (LED), but it can also be other emitters, such as asolid-state laser or organic light emitting diode. The lamp 10 furthercomprises a complimentary second light emitter 14 that emits in the redwavelength spectrum and is also preferably a LED, but can also be asolid-state laser or organic light emitting diode.

The details of operation and fabrication of conventional LEDs are knownand are only briefly discussed. Conventional LEDs can be fabricated froma number of material systems by known methods, with a suitable methodbeing fabrication by Metal Organic Chemical Vapor Deposition (MOCVD).LEDs typically have an active layer sandwiched between two oppositelydoped layers that are either doped p-type or n-type. The top layer ofthe LED is usually p-type and bottom layer 13 is usually n-type,although LEDs also work if the layers are reversed. The p-type andn-type layers have respective contacts that each have a lead to apply abias across p- and n-type layers. This bias results in the active layeremitting light omnidirectionally. The entire LED can be grown on asubstrate.

The first and second LEDs 12, 14 are mounted on a submount 16 formechanical stability. The submount 16 can also contain electricalcircuitry for controlling the relative amount of current or powerapplied to the respective LEDs 12, 14, or to otherwise modify theelectric signal applied to the LEDs 12, 14. The submount 16 can alsocontain components and circuitry to make the lamp resistant toelectrostatic shock. Depending on the particular embodiment, one or bothof the LEDs 12, 14 can be in electrical contact with the submount 16.The submount 16 is mounted at the horizontal base 17 of “metal cup” 18that typically has conductive paths (not shown) for applying a biasacross the contacts on the LEDs 12, 14, to cause each of the LEDs toemit light.

The bias can either be applied directly to the LEDs along the conductivepaths or it can be applied to the LEDs fully or partially through thesubmount 16 and its electronic circuitry. The cup 18 can have areflective surface 20 that reflects light emitted from the LEDs 12,14 sothat it contributes to the light emitted from the lamp 10.

The lamp 10 further comprises a conversion material 22 that surroundsthe first UV emitter 12 except for the surface of the emitter 12 that isadjacent to the submount. The material 22 can be one or more flourescentor phosphorescent material such as a phosphor, flourescent dye orphotoluminescent semiconductor. The material 22 absorbs at least some ofthe electromagnetic radiation (light) emitted by the UV LED 12 andre-emits at least some of the absorbed radiation at one or morewavelength spectrums that are different from the absorbed wavelength. Inthe case of the UV emitter 12, the conversion material 22 has acombination of materials that absorb UV light and re-emit light in thegreen and blue wavelength spectrums. Different materials can be used forabsorbing the UV light and re-emitting green light, with a preferredmaterial being a Sr:thiogallate phosphor. Different materials can alsobe used for absorbing UV light and re-emitting blue light, with apreferred material being ZnS or BaMgAl₁₀O₁₇ doped with appropriateimpurities. The LEDs 12,14, submount 16, and conversion material 22 canbe encased in and protected by a clear epoxy 24 that fills the metal cup16.

When the appropriate electrical signal is applied to the lamp 10, the UVand red LEDs 12, 14, emit light at their respective characteristicspectrum. At least some of the UV light is absorbed by the conversionmaterial 22 and re-emitted as green and blue light. The combination ofblue, green light from the conversion material, and red light from thered LED, provides white light with high efficacy and color renderingthat appears white when viewed by the human eye.

The lamp 10 shows the combination of a blue and green light beingre-emitted from the conversion material, but in an alternativeembodiment according to the present invention, a yellow emittingphosphor can be used instead of green. A full range of broad yellowspectral emission is possible using phosphors based on the (Gd, Y)₃(Al,Ga)₅O₁₂:Ce system. These phosphors are stable and typically display highconversion efficiency when excited using UV light. The combination oflight from these phosphors, along with light from the blue emittingphosphor and red LED provide a versatile white lamp with high efficacyand high color rendering.

Using a UV emitter 12 with a conversion material 22 to convert UV toblue/green or blue/yellow light has a number of advantages. Higherefficiency UV emitters are available compared to blue or green emittersand in the case of solid-state lasers, short wavelength lasers are moreeasily achieved than blue lasers. Also, a wider variety of highefficiency phosphors are available which can be excited by shortwavelength radiation (250–400 nm).

FIG. 2 shows another embodiment of a solid state white lamp 30 accordingto the present invention. It has the same submount 16, first UV LED 12,second red LED 14, metal cup 18 and epoxy 24. However, the lamp 30 has aconversion material 32 that covers both the UV and red LEDs 12, 14, withthe conversion material absorbing the UV light and re-emitting in theblue and green wavelength spectrum. Most of the light emitted by the redLED is not absorbed by the conversion material, and passes through tocontribute to emission by the lamp 30.

To maximize the uniformity of the overall emission from the lamp 30(color as a function of viewing angle) the UV and red LEDs 12, 14 can beplaced as close together as practical. By covering both the LEDs 12, 14with the conversion material 32, the manufacturing problems and reducedyield associated with covering only one LED, can be avoided. However,covering the red LED with the conversion material may result in some ofthe red light being absorbed as it passes through the conversionmaterial.

FIGS. 3 and 4 show additional embodiments of a lamp 40, 60, according tothe present invention, with each of the lamps having a UV emitter 42,used in combination with complimentary green and red emitters 44, 46.The emitters are preferably LEDs, although other devices can also beused. Each of the LEDs 42, 44, 46 is mounted on a submount 48 similar tothe submount 16 in FIGS. 1 and 2, and in each embodiment the submount 48is mounted at the base of a metal cup 50 that is similar to the metalcup 18 in FIGS. 1 and 2. The cup 50 includes conductive paths (notshown) for applying a bias across the LEDs 42, 44, 46, to cause each ofthem to emit light. The bias can either be applied directly to theemitters or can be applied through the submount 48 and its electroniccircuitry. The lamps 40 and 60 can also be encased in an epoxy 54 thatfills the cup 50 to cover and protect the lamp components.

With the appropriate signal applied to the lamp 40 in FIG. 4, the LEDs42, 44, 46 produce light at their respective wavelength spectrum. The UVemitter 42 is covered by a blue conversion material 52 made of ZnS orBaMgAl₁₀O₁₇ doped with appropriate impurities or another suitableblue-converting material, such that at least some of the UV light fromthe UV emitter 42 is absorbed by the conversion material 52 andre-emitted as blue light. The lamp 40 simultaneously radiates blue,green and red light, which combine to produce a white light having highefficacy and high color rendering.

In the lamp 60 of FIG. 4, all of the LEDs 42, 44, 46 are covered by theblue conversion material 56. Light from the UV LED 42 is absorbed by theconversion material 56 and re-emitted as blue light. Most of the lightfrom the green and red LEDs 44, 46 passes through the conversionmaterial 56 without being absorbed, such that the lamp 60 emits a whitecombination of the blue, green and red light.

FIGS. 5 and 6 show additional embodiments of a lamp 70, 90, according tothe present invention, with each having a UV emitter 72, used incombination with a blue emitter 74 and a red emitter 76. Each of theemitters 72, 74, 76 is preferably an LED and each is mounted on asubmount 78 similar to the submount 16 in FIGS. 1 and 2. In eachembodiment the submount 78 is mounted at the base of a metal cup 80 thatis similar to the cup 18 in FIGS. 1 and 2. Conductive paths (not shown)are included for applying a bias across the LEDs 72, 74, 76, to causeeach of them to emit light. Each of the lamps also includes a clearepoxy 82 to cover and protect the lamp components.

In lamp 70, the UV LED 72 is covered by a conversion material 84 (e.g.thiogallate phosphor) that absorbs UV light and re-emits green light. Inlamp 90 a similar conversion material 86 covers the UV LED 72 and alsocovers the red and blue LEDs 74, 76. For lamps 70, 90 the LEDs 72, 74,76 emit in their respective wavelength spectrums when a bias is appliedand the UV wavelength light from each UV LED 72 is absorbed by therespective conversion material 84, 86 and re-emitted as green light. Inlamp 70 the green light combines with the direct light from the blue andgreen emitters 74, 76. In lamp 90 the green light combines with the blueand red light that passes through the conversion material 86. In eithercase, the lamps 70, 90 emit a white light combination of red, blue andgreen.

Depending on the application of each of the lamp embodiments describedabove, it may be desirable to arrange the particular conversion materialsuch that it absorbs essentially all of the UV light from its particularUV emitter. UV light is not useful for illumination and at certainintensity levels can be harmful to eyes or skin.

In the embodiments above a single LED is shown for each type of LED, butthe optimal arrangement may require a plurality of LEDs of one or bothtypes. Further, the LEDs shown can have larger or smaller emissionareas.

Solid State Laser Emitters

FIG. 7 shows another embodiment of a lamp 100 according to the presentinvention. It comprises a solid-state laser 102 and a complimentarysecond emitter 106 that are both mounted to a submount 108 similar tothe submounts described above. Conductive paths can be included to applya bias across the laser 102 and second emitter 106, and the device canthen be mounted to the bottom of a metal cup 110, filled with epoxy. Aconversion material 104 is included that covers the laser 102 andabsorbs blue light and re-emits in a different wavelength spectrum thanthe light from the laser 102.

For the lamp 100, the laser 102 preferably emits blue wavelengthspectrum, although other types of lasers can be used. The conversionmaterial 104 is preferably made of a material that absorbs blue lightand re-emits green light. The emitter 106 is preferably a LED that emitsin the red light spectrum. When a bias is applied across the laser 102and the LED 106, the laser 102 emits in the blue light wavelengthspectrum and a suitable amount of conversion material 104 is included sothat less than all of the blue light is absorbed by the conversionmaterial 104 and some of the blue light passes through. The red LED 106emits red light and the conversion material 104 re-emits green lightsuch that the lamp 100 emits a white light combination of the red, greenand blue light, with high efficacy and good color rendering.

Lasers have the advantage of emitting a coherent light source that canbe selectively scattered or directed. As lasers are further developedthey may become preferable over LEDs, because they have the potentialfor higher efficiency and higher output than LEDs.

FIG. 8 shows another lamp 120 according to the present invention that issimilar to the lamp 100 in FIG. 7. It includes a blue emitting laser 122and a red emitter 124 that is preferably a LED. The laser 122 and redLED 124 are mounted to a submount 123, and the submount 123 can then bemounted to the bottom of a metal cup 128. In lamp 120, the blue laser122 is covered by a yellow conversion material 130 that absorbs bluelight and re-emits yellow light. When the laser 122 and red LED 124 areemitting, the yellow conversion material 130 absorbs some of the bluelight and emits yellow light such that the lamp 100 emits a white lightcombination of blue, yellow and red light having good efficacy and colorrendering.

For each of the embodiments described, the conversion material can coverthe laser and complimentary LED. For instance, FIG. 9 shows anotherembodiment of a lamp 140 according to the present invention thatincludes a blue emitting laser 142 and a red emitting LED 144 mounted ona submount 146. A conversion material 148 covers the laser 142 and thered LED 144. The conversion material 148 contains material that absorbssome of the lasers blue light and re-emits green (or yellow). Most ofthe light from the red LED 144 passes through the conversion material148 such that the lamp 140 emits a white light combination of blue,green (or yellow) and red light.

Many different types of lasers and LEDs can be used that emit indifferent wavelength spectrums. Many different combinations of laserembodiments of lamps according to the present invention can be realizedwith many different numbers of lasers or LEDs. For example, FIG. 10shows another embodiment of a similar lamp 150 according to the presentinvention having two blue emitting LEDs 152 between two red solid-statelasers 154. The blue LEDs 152 are covered by a conversion material 156that absorbs blue light and re-emits green light. As the LEDs 152 andlasers 154 emit light, the conversion material absorbs some of the bluelight such that the lamp 150 emits a white light combination of blue,green and red light. In an alternative embodiment (not shown), theconversion material 156 covers the blue LEDs 152 and the red lasers 154.Alternatively, blue LEDs may be combined with red lasers, with at leastsome of the light emitted from the blue laser converted to light ofanother wavelength by a downconverting media according to the presentinvention.

Large Area Emitters Combined With Multiple Emitters

The prior art lamps, as well as some of the lamps described above, canproduce a projected light that can have an asymmetric appearance. Forinstance, lamp embodiments with a blue emitter, conversion material, andred emitter, can appear as though the projected light is more red on oneside and more blue on the other.

This is a particular problem with large area LEDs that are useful forhigh-power, high output lamps. Higher current levels can be applied tolarger LEDs which results in higher luminous flux. Multiple large areaLEDs can be used in solid-state lamps that can operate at high powerlevels up to 5–70 Watts and beyond. When complimentary LEDs are placedside by side to the large area LED, the lamp tends to produce whitelight that is not balanced.

To help provide a more symmetric appearance to the projected light,multiple complimentary LEDs can be used to surround each large area LED(or to surround a group of large area LEDs) such that the high luminousflux of the large area LED is balanced by the surrounding LEDs. Thistype of arrangement in a single package can also provide advantages inheat sinking, compactness and color mixing.

To illustrate this arrangement, FIGS. 11 and 12 show a lamp 160according to the present invention having a large area LED 162surrounded by a plurality of complimentary LEDs 164. The LEDs aremounted to a submount 166, which can then be mounted to the base of ametal cup 167. Many different large area LEDs can be used, with asuitable large area LED 164 being a blue emitting LED. A conversionmaterial 168 covers the LED 162 with the preferred conversion material168 absorbing the blue light and re-emitting yellow light. In anotherembodiment of the lamp 160, the conversion material 168 absorbs bluelight and re-emits green light. The surrounding LEDs 164 emit red lightand are spaced around the LED 162 in a sufficient number to provide abalance to the high flux of the LED 162 such that the lamp emits abalanced white light. The lamp 160 has four surrounding LEDs 164 aroundthe large area LED 162, but a different number of surrounding LEDs 164can be used depending on the intensity of the large area LED 162, andthe size and intensity of the surrounding LEDs 164. When the large areaLED 162 and surrounding LEDs 164 are emitting, the lamp 160 emits abalanced white light combination of the blue, green and red light.

Similar to the embodiments above, the components of the lamp 160 can beencased in epoxy 169 and the submount 166 and/or metal cup 167 can haveconductors to apply a bias to the LEDs 162, 164. Also, in alternativeembodiments of the lamp 160, the conversion material can cover all theLEDs 162, 164 and different colors of LED 162, 164 can be used.

Scattering Particles

To improve the uniformity of light emitting from the lamps describedabove, it can be desirable to scatter the light as it emits from thevarious emitters. One way to scatter light is by using scatteringparticles that randomly refract light. To effectively scatter light, thediameter of these particles should be approximately one half of thewavelength of the light being scattered. In air, this would result inthe particles being approximately 0.2 to 0.25 microns in diameter andthe diameters would be smaller if the particles are in a medium having adifferent index of refraction than air such as epoxy.

In the lamps described above, a conversion material typically surroundsat least one of the emitters and typically comprises phosphor particles.The conversion efficiency of phosphors generally decreases as the sizeof the phosphor particles decrease. As a result, it is difficult toobtain high conversion efficiency phosphors particles that are smallerthan approximately 1 micron in diameter, making phosphor particlesgenerally too large to effectively scatter light.

To produce more uniform light emission in white emitting lamps describedabove (and prior art lamps) scattering particles can be included suchthat light from the emitters passes through them and is refracted to mixthe light and provide an overall light emission that is more uniform incolor and intensity. The scattering particles can be arranged indifferent locations, such as in the conversion material or epoxy, or theparticles can form their own layer. The preferred scattering particleswould not substantially absorb light at any of the wavelengths involvedand would have a substantially different index of refraction than thematerial in which it is embedded (for example, epoxy) The scatteringparticles should have as high of an index of refraction as possible.Suitable scattering particles can be made of titanium oxide (TiO₂) whichhas a high index of refraction (n=2.6 to 2.9) and is effective atscattering light. Since the primary requirement for the scattering“particles” is that they have a different index of refraction from theirsurrounding material and that they have a particular size range, otherelements such as small voids or pores could also be used as “scatteringparticles”.

FIG. 13 shows one embodiment of a lamp 170, according to the presentinvention, having a UV emitting LED 172 and red emitting LED 174 mountedon a submount 176 along with the necessary conductive paths. Aconversion material 178 is included that covers both the UV and red LEDs172, 174 such that light from the LEDs passes through the conversionmaterial 178. The conversion material 178 contains scattering particles180 disposed to refract the light passing through the conversionmaterial 178. Each of the scattering particles 180 can be similarlysized so that they primarily scatter a single wavelength of light, suchas from the UV LED 72, or they can have different sizes to scatter lightof different wavelengths of light, such as from the LEDs 172, 174 andthe conversion material 178. Like the embodiments above, the LEDs 172,174, conversion material 178, and submount 176 are in a metal cup 182and are encased in an epoxy 184.

FIGS. 14 and 15 show two additional embodiments of a lamp 190, 200,according to the present invention. Each lamp 190, 200 has a UV and redLED 172, 174, a submount 176, and a conversion material 178, all ofwhich are in a metal cup 182 and epoxy 184. However, for lamp 190, thescattering particles 192 are disposed in the epoxy 184. For lamp 200,the scattering particles 194 are formed in a layer on top of the epoxy184. The light from the LEDs 172, 174 and conversion material 176 passesthrough the scattering particles 192, 194 where different wavelengths oflight can be refracted depending on the size and material of theparticles 192, 194. Like the lamp 170 in FIG. 13, the scatteringparticles 192, 194 can be similarly sized or can have different sizesdepending on the wavelength of light emitted from the LEDs 172, 174 andthe conversion material 176.

Miscellaneous Features

Other lamp features according to the present invention can improve lightextraction from the lamps described above. FIG. 16 shows anotherembodiment of a lamp 210 according to the present invention having aclear material 212, such as an epoxy, arranged over the emitters 214,216, which in this embodiment are UV and red emitting LEDs respectively.The material 212 preferably forms a hemispheric volume with the LED 212,216 as close as practical to the origin of the hemisphere. Thehemisphere should have a large radius compared to the dimensions of theLEDs. The material 212 preferably has an index of refractionapproximately the same as the primary surfaces of the LEDs 214, 216 fromwhich most of the light is emitted (e.g. the substrate for flip-chipLEDs or the top surface for a standard LED). A layer of conversionmaterial 218 is then included on the surface of the clear layer 212.This arrangement minimizes reflection of light at the interface betweenthe LED surfaces and the clear layer 212, and the clear layer 122 andlayer of conversion material 218, back into the LED active layers wherethe light can be absorbed.

In the lamp embodiments according to the present invention, theintensities of the individual LEDs (and lasers) can be controlled. Thiscan be accomplished by controlling the relative emission of the LEDsthrough control of the applied current, and controlling the blue/greenemission of the conversion material by controlling the amount andlocation of the conversion material. This type of control allows thelamps to emit at color points not accessible using the blue LED/yellowphosphor approach. This control/adjustability could also enhancemanufacturing yield by selecting and matching the emissioncharacteristics of the different LEDs (peak emission wavelength, etc.),thereby allowing the fabrication of lamps having very tight spectraldistribution (color, hue, etc.) over a large range of color temperature.Similarly, by controlling the relative power applied to the respectiveLEDs or the amount of phosphor applied, a large range of flexibility isavailable both for providing the desired chromaticity and controllingthe color output of the individual devices. A lamp according to theinvention could be provided that allows the end user to control therelative powers applied to the respective LEDs. The lamp could be“tuned” by the user to achieve desired colors or hues from a singlelamp. This type of control can be provided by known control electronics.

The lamps according to the present invention can also include lenses andfacets to control the direction of the lamp's emitting light. Othercomponents could be added related to thermal management, opticalcontrol, or electrical signal modification and control, to further adaptthe lamps to a variety of applications.

Although the present invention has been described in considerable detailwith reference to certain preferred configurations thereof, otherversions are possible. As mentioned above, different LEDs that emit atdifferent colors can be used in embodiments described above. In thoseembodiments where one emitter is described as providing light in aparticular wavelength spectrum, two or more emitters can be used. Theconversion materials described above can use many different types ofmaterial that absorb different wavelengths of light and re-emitdifferent wavelengths beyond those described above. Therefore, thespirit and scope of the appended claims should not be limited to theirpreferred versions contained therein.

1. A white light emitting lamp, comprising: a solid state ultra violet (UV) emitter emitting light in the UV wavelength spectrum; a conversion material at least partially covering said UV emitter and arranged to absorb at least some of the light emitting from said UV emitter and re-emit light at one or more different wavelength spectrums of light; and one or more complimentary solid state emitters substantially uncovered by said conversion material and emitting different wavelength spectrums of light than said UV emitter and said conversion material, said lamp emitting a white light combination of light emitted from said complimentary emitters and from said conversion material, said white light having high efficacy and good color rendering; said UV and complimentary emitters being mounted in a reflector element having conductors to apply a bias to said emitters, said bias causing said emitters to emit light.
 2. The lamp of claim 1, wherein said UV emitter comprises a UV emitting light emitting diode (LED), said conversion material absorbs at least some of the light emitting from said UV LED and re-emits wavelengths of light in the blue and green spectrum.
 3. The lamp of claim 1, wherein said one or more complimentary emitters comprise a LED emitting a wavelength of light in the red spectrum.
 4. The lamp of claim 1, wherein, said UV emitter comprises a UV emitting LED and said conversion material absorbs at least some of the light emitting from said UV LED and re-emits wavelengths of light in the blue spectrum.
 5. The lamp of claim 1, wherein said one or more complimentary emitters comprise a LED emitting a wavelength of light in the green spectrum and a LED emitting a wavelength of light in the red spectrum.
 6. The lamp of claim 1, wherein said UV emitter comprises a UV emitting LED and said conversion material absorbs at least some of the light emitting from said UV LED and re-emits wavelengths of light in the green spectrum.
 7. The lamp of claim 1, wherein said one or more complimentary emitters comprises a LED emitting a wavelength of light in the green spectrum and a LED emitting a wavelength of in the red spectrum.
 8. The lamp of claim 1, wherein said conversion material covers both said UV emitter and said one or more complimentary emitters, most of the light from said complimentary emitters passing through said conversion material without being absorbed.
 9. The lamp of claim 1, wherein said UV and complimentary emitters are mounted on a submount.
 10. The lamp of claim 1, wherein said UV and complimentary emitters each comprise an emitter from the group consisting of an LED, a solid state laser, and organic light emitting diode.
 11. A white light emitting lamp, comprising: a solid state ultra violet (UV) emitter emitting light in the UV wavelength spectrum; a conversion material arranged to absorb at least some of the light emitting from said UV emitter and re-emit light at one or more different wavelength spectrums of light; one or more complimentary solid state emitters emitting different wavelength spectrums of light than said UV emitter and said conversion material, said lamp emitting a white light combination of light emitted from said complimentary emitters and from said conversion material, said white light having high efficacy and good color rendering, said UV and complimentary emitters being mounted in a reflector element having conductors to apply a bias to said emitters, said bias causing said emitters to emit light; and scattering particles arranged to scatter the light from said UV and complimentary emitters to produce a substantially uniform emission of white light from said lamp, said scattering particles each having a diameter of approximately one half a wavelength of light emitted by either said UV emitter or said complimentary emitters.
 12. A white light emitting lamp, comprising: a solid state ultra violet (UV) emitter emitting light in the UV wavelength spectrum; a conversion material arranged to absorb at least some of the light emitting from said UV emitter and re-emit light at one or more different wavelength spectrums of light; one or more complimentary solid state emitters emitting different wavelength spectrums of light than said UV emitter and said conversion material, said lamp emitting a white light combination of light emitted from said complimentary emitters and from said conversion material, said white light having high efficacy and good color rendering, said UV and complimentary emitters being mounted in a reflector element having conductors to apply a bias to said emitters, said bias causing said emitters to emit light; and a layer of clear material between said UV emitter and said conversion material, said clear layer forming a hemispheric or sheet volume.
 13. The lamp of claim 12, wherein said layer of clear material has an index of refraction approximately the same as that of the emitting surface of said UV emitter.
 14. A white light emitting lamp, comprising: a solid state ultra violet (UV) emitter emitting light in the UV wavelength spectrum; a conversion material arranged to absorb at least some of the light emitting from said UV emitter and re-emit light at one or more different wavelength spectrums of light; and one or more complimentary solid state emitters emitting different wavelength spectrums of light than said UV emitter and said conversion material, said lamp emitting a white light combination of light emitted from said complimentary emitters and from said conversion material, said white light having high efficacy and good color rendering, said UV and complimentary emitters being mounted in a reflector element having conductors to apply a bias to said emitters, said bias causing said emitters to emit light, wherein the intensities of the light emitted from said UV emitter and complimentary emitters can be independently varied to vary the color or hue of white light emitted from said lamp.
 15. The lamp of claim 1, further comprising a component to control the direction of light emitted from said lamp.
 16. The lamp of claim 1, wherein said conversion material comprises a material from the group consisting of a phosphor, fluorescent dye, photoluminescent semiconductor, and combinations thereof.
 17. The lamp of claim 1, wherein said conversion material absorbs substantially all the light emitting from said UV emitter.
 18. The lamp of claim 1, wherein said UV emitter comprises a plurality of large area LED and said complimentary emitters comprise a plurality of LEDs surrounding said large area LED, said lamp emitting a balanced white light.
 19. A white light emitting lamp, comprising: a solid state laser emitting light in a first wavelength spectrum; a conversion material at least partially covering said solid state laser and arranged to absorb at least some of the light emitting from said laser and re-emit light at one or more different wavelength spectrums of light; and one or more complimentary solid state emitters emitting different wavelengths of light than said laser and said conversion material, said lamp emitting a white light combination of light emitted from said laser, complimentary emitters, and conversion material, said white light having high efficacy and good color rendering; said laser emitting light in the blue wavelength spectrum, said conversion material absorbing some of the light emitting from said laser and re-emitting a wavelength of light in the green spectrum, the non-absorbed blue light passing through said conversion material.
 20. The lamp of claim 19, wherein said one or more complimentary emitters comprise a LED emitting a wavelength of light in the red spectrum.
 21. The lamp of claim 19, wherein said conversion material absorbs some of the light emitting from said laser and re-emits a wavelength of light in the blue and yellow spectrum, the non-absorbed blue light passing through said conversion material.
 22. The lamp of claim 19, further comprising a submount and metal cup, said laser and complimentary emitters mounted on said submount and said submount mounted in said reflector element.
 23. The lamp of claim 19, further comprising scattering particles arranged to scatter the light from said laser and complimentary emitters to produce a more uniform emission of white light from said lamp.
 24. The lamp of claim 19, wherein the intensities of the light emitted from said laser and complimentary emitters can be independently varied to vary the color or hue of white light emitted from said lamp.
 25. The lamp of claim 19, wherein said conversion material comprises a material from the group consisting of a phosphor, fluorescent dye, photoluminescent semiconductor, and combinations thereof.
 26. A white light emitting lamp, comprising: a first solid state emitter emitting light in a first wavelength spectrum; a conversion material to absorb at least some of the light from said first solid state emitter, and emit light at one or more different wavelength spectrums; one or more complimentary emitters each of which emits light at a wavelength spectrum different from said first wavelength spectrum and said conversion material wavelength spectrums; and scattering particles arranged to scatter the light from said first emitter, conversion material and complimentary emitters, said lamp emitting a uniform white light combination of light from said first emitter, conversion material and complimentary emitters; said scattering particles each having a diameter of approximately one half a wavelength of light emitted by either said first emitter, conversion material or complimentary emitters.
 27. The lamp of claim 26, wherein said scattering particles are disposed within said conversion material.
 28. The lamp of claim 26, further comprising a clear encapsulant material, said encapsulant encasing at least part of said lamp with at least some of the light from said first emitter, conversion material and complimentary emitters passing through said encapsulant, said scattering particles disposed within said encapsulant.
 29. The lamp of claim 26, wherein said scattering particles form a layer of scattering particles with at least some of the light from said first emitter, conversion material and complimentary emitters passing through said layer.
 30. The lamp of claim 26, wherein the white light emitted by said lamp has high efficacy and good color rendering.
 31. A high flux white emitting lamp, comprising: a large area light emitting diode (LED) emitting light at a first wavelength spectrum; a conversion material arranged to absorb at least some of the light from said large area LED, and re-emit at least one wavelength light in a spectrum different from said first wavelength spectrum; and a plurality of complimentary solid state emitters surrounding said large area LED and each emitting light in a spectrum different from said large area LED and said conversion material, said lamp emitting a balanced and uniform white light combination of light from said large area LED, conversion material and complimentary emitters, said white light having high efficacy and good color rendering; said conversion material covering both said large area LED and said plurality of complimentary emitters, most of the light from said complimentary emitters passing through said conversion material without being absorbed.
 32. The lamp of claim 31, further comprising a submount and reflector element, said large area LED and complimentary emitters mounted on said submount and said submount mounted in said metal cup.
 33. The lamp of claim 31, further comprising scattering particles arranged to scatter the light from said large area LED and complimentary emitters to produce a substantially uniform emission of white light from said lamp.
 34. The lamp of claim 31, wherein the intensities of the light emitted from said large area LED and complimentary emitters can be independently varied to vary the color or hue of white light emitted from said lamp.
 35. The lamp of claim 31, wherein said large area LED comprises a plurality of large area LEDs.
 36. A method for producing white light with high efficacy and good color rendering, comprising: generating light in the UV wavelength spectrum from a UV light source; passing said UV light through a conversion material in contact with said UV light source that absorbs said UV light and re-emits light at one or more different wavelength spectrums; generating complimentary light at one or more wavelength spectrums that is different from said conversion material wavelength spectrums; combining said conversion material light and said complimentary light to generate white light with high efficacy and good color rendering; and providing reflective element that reflects said UV light, complimentary light and conversion material light such that all contribute to light emission direction, said reflective element also comprising a means for causing said light generation.
 37. The method of claim 36, further comprising scattering said conversion material light and said complimentary light to generate substantially uniform white light.
 38. A method for producing white light with high efficacy and good color rendering, comprising: generating laser light from a laser light source; passing said laser light through a conversion material at least partially covering said laser light source that absorbs at least some of said laser light and re-emits light at one or more different wavelength spectrums; generating complimentary light at one or more wavelength spectrums that is different from said conversion material wavelength spectrums; and combining said conversion material light and said complimentary light to generate white light with high efficacy and good color rendering, said laser light being blue light, said conversion material absorbing some of the light emitting from said laser and re-emitting a wavelength of light in the green spectrum, the non-absorbed blue light passing through said conversion material. 